Snowgrasses

The larger alpine tussock grasses, or 'snow grasses' as they are called, are frequently a metre high and sometimes as wide. Under good conditions they may reach head height at up to 2 m. Growth is slow and some of the larger specimens are estimated to be several centuries old.¹³⁷ The more or less hemispherical form of many of the snow tussocks confers on the mountain slopes a very distinctive and attractive texture reminiscent of that of cirrus clouds or, when the tussocks are tossed by the wind, waves of the sea. The colour of a snow tussock landscape is generally not green, but, depending on the species, ranges from a pale straw colour through shades of brown to a distinctly reddish shade. The lack of greenness results partly from the regular dying back

Figure 96 The snow tussock (Chionochloa macra) with flower heads of the spaniard (Aciphylla scott-thomsonii). Old Man Range, Otago.
Photo: J. W. Dawson.

page 173of the leaves from the tips and partly to the presence of masking pigments. Heavy flowering seasons of the snow grasses are sporadic and often coincide with those of the beech species. This suggests that snow grasses too require a warm summer preceding flowering for the initiation of flower buds.

The flower and seed heads of some of the larger snow tussocks are quite diffuse, and their very slender stems and small, scattered, pale, flower or seed heads give an insubstantial misty effect similar to that of the garden Gypsophila, so popular in flower arrangements. On the wetter western mountains of the South Island the broadleaved snow tussock (C. flavescens), can grow sometimes 2 m high, and dominates in the zone 200 m above treeline. The mid-ribbed snow tussock (C. pallens) is often present, generally on younger, better drained soils. Both species are also common on the North Island axial ranges. With increasing altitude on the wet South Island mountains the two large snow tussocks gradually give way to the much smaller curled snow tussock (C. crassiuscula).

On Mt. Taranaki (Egmont) and the central volcanoes in the North

Figure 97 Dense cover of red tussock (Chionochloa rubra) on a swampy valley floor. Near Boulder Lake, north-west Nelson.
Photo: J. W. Dawson.

page 174Island the only snow tussock present is red tussock (C. rubra), which occupies a wide range of habitats in the herbfield zone. In the South Island on the wetter mountains red tussock is abundant only at or below the treeline on poorly drained and frosty flat valley floors. With its large size and strong reddish colouration it provides an impressive sight (Fig. 97).

On the drier eastern South Island mountains in the southern half, the dominant snow tussock in the low alpine zone is the narrow-leaved snow tussock (C. rigida). This gives way at higher altitudes to the smaller recently described slim snow tussock (C. macra). Only slim snow tussock extends north of the central South Island and it then occupies a broader altitudinal zone.

Among the smaller species of Chionochloa, which are found mostly at higher levels in herbfield, carpet grass (C. australis) is worth a special mention. As its common name indicates it does not have a tussock habit, but forms thick, often extensive swards. The needle-like leaves are dark green and shiny and as they are also slippery and tend to lie downhill, they need to be walked on with care. Carpet grass is found on wetter mountains in the northern third of the South Island.

Where snow tussocks are tall and dense near the treeline one might think there would be little room left for other alpine herbs; in fact there are quite a number. Some are small and inconspicuous, enjoying the shelter and tolerating the shade of the tussocks. Others are much more conspicuous and could be termed large or even giant herbs approaching or exceeding the tussocks in height.